March 5, 2011

PAUL SMITHS - One of the worst droughts in the past 50,000 years was probably connected to ice sheet collapse and melting at the end of the last ice age, Paul Smith's College Professor Curt Stager has found.

Stager's findings were published last week in the online version of the journal Science.

Based on sediment cores collected from lakes as well as dozens of other geological records from most of Africa and southern Asia, an international team of paleoclimatologists, headed by Stager, documented a centuries-long drought that struck tropical monsoon regions 16,000 to 17,000 years ago - about the same time an influx of icebergs and meltwater surged into the North Atlantic.

Article Photos

Curt Stager(Photo courtesy of Paul Smith’s College)

This is the first study to show how exceptionally widespread and severe the drought was.

The drought likely brought deep-seated change to Stone Age societies affected by it, disrupting migration patterns and reducing populations. Lake Victoria in east-central Africa, the world's largest tropical lake, dried out during the episode; the other major feeder of the Nile, Lake Tana in modern-day Ethiopia, also went dry. The Nile, Congo, Indus and other major rivers were affected.

The exact causes of the so-called "H1 megadrought" are still in question. But its timing suggests that it was somehow linked to the addition of ice and meltwater into the North Atlantic when the planet was emerging from the last ice age. That sudden deglaciation caused temperatures in Europe and much of Asia to drop, thereby disrupting climate systems that brought seasonal rains to Africa and southern Asia. Those systems worked by wicking moisture from oceans during hot summers and returning the water as rain. When temperatures cooled, the moisture never made it into the atmosphere.

The research was sponsored by the National Science Foundation and other international research organizations.

Could climate change today lead to such a cataclysmic drought again?

"Hopefully not," says Stager, who noted that not nearly as much unstable ice remains within range of the critical North Atlantic region today. "But it would certainly have been an important chapter in early human history, and one that hasn't been fully recognized yet."